Process for the manufacture of preserved food products



Feb. 6, 1945. PEEBLES 2,368,945

I PRocEss FOR THE MANUFACTURE OF PRESERVED FOOD PRODUCTS Filed July 31,1940 IINVENTOR fla /d fl. Peek/65 ATTOR N E Y stantial rest or storageof the hot material.

Patented Feb. 6, 1945 PROCESS FOR THE MANUFACTURE OF PRESERVED FOODPRODUCTS David D. Peebles, Berkeley, Calif; minor to Golden StateCompany, Ltd., San Francisc Calii'., a corporation of DelawareApplication July 31, 1940, Serial No. 348,979

4 Claims.

This invention relates generally to processes for the manufacture offood products, particularly products of paste-like form. Morespecifically, the process is applicable to the processing and canning oftomato paste.

In the preparation of tomato paste, it has been common practice'toeither concentrate the pulp by open kettle evaporation, or by vacuumevaporation. Evaporation in open kettles gives the paste a desirablebody, but impairs color and like heat sensitive properties. By desirablebody, I have reference to the ability of a final product containing atleast 25% solids to stand up when poured out on a flat surface, and tohave a grainy surface texture. Vacuum evaporation is capable ofproducing a paste without serious color impairment, but will not producea product having the desired body. Because of serious color impairmentwith open kettle evaporation, it has been common practice to introduceartificial coloring materials in order to simulate a natural freshcolor. a o

I have found that the natural fresh color of tomato paste or likematerial, and other desirable heat sensitive properties, can be retainedby proper treatment of the material prior to introducing the paste intocans, and at the same time the desired body can also be imparted to theproduct. It is consequently an object of the present invention toprovide such an improved process, applicable particularly to tomatopaste, but which can also be used on related products involving somewhatthe same problems.

In carrying out the present process, I first form a suitable pulp of thematerial which is to be preserved, as for example tomatoes. Thus thetomatoes can be crushed or passed through a suitable pulping machine,and the skins and seeds removed by suitable separating equipment. Thetomato pulp is then subjected to an evaporating operation which may becarried out in a number of stages, but which proceeds substantiallycontinuously at a rapid rate without sub- The type of evaporatingequipment which is best suited for this purpose is one in which thematerial passes at high velocities through relatively long evaporatingtubes.

I have found it particularly desirable to carry out the last stage ofevaporation by use of equipment such as illustrated in the accompanyingdrawing. To briefly describe this equipment, it consists of two groupsof evaporating tubes A and B. The upper ends of these tubes are attachedto a tube sheet l0, and the lower ends to the tube sheet ll. Surroundingthe evaporator tubes A and B there is a heater Jacket l2 into whichsteam can be introduced through the pipe connection l3.

Extending upwardly within the steam Jacket l2, there is a conduit orshroud H, which surrounds the two groups of evaporating tubes. Steamintroduced through pipe l3 flows upwardly between the conduit I l andthe outer walls of the jacket I2, before contacting the evaporatingtubes, after which the steam flows downwardly about the evaporatingtubes to a point near the lower end of these tubes, where condensate isdrained away through pipe i6. Below the tube sheet I I there is aseparating chamber H, which serves to receive material discharged fromthe lower ends of the evaporating tubes B, and which serves the purposeof separating liquid from vapor. Pipe i8 is a vapor outlet from chamberI1, and a pipe l9 at the lower end of chamber i1 is for the purpose ofdraining away concentrate. Chamber 2| is secured to the lower side oftube sheet i l, and communicates with the inner group of evaporatingpipes A. The liquid to be concentrated is introduced into chamber 2|through pipe 22. Pipe 20 serves to carry away non-condensable gases fromthe upper part of the heating J acket.

Above the tube sheet i0 and communicating with the upper ends of all ofthe'evaporating tubes, there is a distributing chamber 28. The purposeof this chamber is to transfer and distribute material discharged fromthe upflow evaporating tubes A to the downiiow tubes B. Note that thischamber 23 is of. substantial height whereby the top wall 24 isconsiderably elevated above the upper ends of the evaporating tubes. Thepurpose of this arrangement is to prevent plastering of the top wall 24,with the material discharged from tubes A, since it has been found thatsuch plastering (which results from the use of a relatively shortchamber 23) prevents proper operation of the evaporator, particularly inthat it makes for uneven distribution of the liquid material into thedownflow tubes B.

In conjunction with chamber 23, I have shown spaced diffusion screens26. These diffusion screens extend across the lower portion of thechamber 23, and are in the path of material discharged from the upperends of the tubes A. They can be made of relatively coarse mesh wire,such as a woven wire screen of one-quarter inch mesh. These screens actin eflect as a brake against upwardvelocity of material, and in additionthey aid in securing uniform distribution of small droplets of liquid tothe tubes B.

As will be evident from the foregoing description, the evaporating cycleof the equipment described involves an upfiow through the tubes A,followed immediately by downflow through the tubes B. In the separator I'I the concentrate separates from vapor and is immediately withdrawnthrough pipe l9. There are in this instance about twice as many downflowtubes B as upfiow tubes, because of the larger volume of vapor passingthrough tubes B.

In operating the above evaporator the mixed vapor-liquid phase materialattains relatively high velocities in the evaporating tubes. As themixed phase material discharges from the upper ends of the tubes A, itis impacted upon the screens 26, and immediately thereafter isdischarged downwardly through the tubes B. There is no plastering of thewalls of chamber 23 with concentrate, and there is a relatively evendistribution in the downflow tubes B, with the liquid phase materialbeing introduced into these tubes in the form of droplets or atomizedparticles. There is a continuous increase in concentration as thematerial passes through the evaporator, and concentrate is notintermingled with more dilute material.

The evaporating tubes are relatively long in order to secure highvelocities and in order to make possible a relatively high degree ofconc'entration-by one pass of the material through the equipment. Forexample, in one installation where the evaporating tubes are 1% inchesinside diameter, they are 20 feet in length. The chamber 23 can vary inheight from say 12 to 36 inches. Greater height can be used if desired.When using the evaporator for the concentration of tomato paste, it isoperated at atmospheric pressure, that is, with the pressure inseparator ll at substantially atmospheric. Steam at suitable pressure issupplied to jacket I 2, as for example about 30 pounds per square inch.Immediately before being introduced through pipe 22 the paste ispreheated to a suitable temperature such as about 180 F.

To continue with the description of my process, the tomato paste can bepassed twice through evaporating equipment of the type. described,whereby assuming that the paste originally contains around 6.5% solids,it is concentrated to, from say about 15 to solids in the first pass. Inthe second pass it can be concentrated to from to 65% solids. It isparticularly desirable that equipment of the type illustrated, involvinghigh velocity flow through long evaporating tubes, be used for the finalstage of concentration. The first stage up to say about 15% solids canbe carried out in conventional vacuum evaporating equipment. Betweenevaporating stages care is taken to avoid storage at high temperaturefor a sufficient length of time to deteriorate color. The entireevaporating procedure is preferably maintained substantially continuousuntil the desired concentrate is obtained.

The paste-like concentrate, as it is removed from the separator I1, isat a temperature depending upon pressures maintained within theevaporator. With operation at atmospheric pressures, the temperaturewill vary from 190' F. to 220 F., depending upon the barometric pressureexisting at the plant location. In a typical instance the temperaturehas been 215 F., and in most instances it will range from 210 F.

to 220 F. Assuming that the temperature is in excess of about 195 F.,the paste is immediately passed through a suitable cooling appliance.The cooler is directly connected with the separator I! so that the pasteis not contacted by air and its sterility is preserved. It serves torapidly reduce the temperature of the paste to a value which is stillcapable of sterilizing, but at which color is not impaired at a rapidrate, as for example 190 F. to 195 F. While at this temperature, it isintroduced into cans by means of suitable canning machinery, andimmediately after the cans are sealed they are tipped over to insureproper sterilization of the' head spaces in the cans. By usingsterilized cans and by preventing introduction of micro-organisms whilethe cans are being filled and sealed, the paste can be cooled to lowertemperatures than those specified, such as F., thus avoiding an extendedcooling period after the cans are filled and sealed.

In the foregoing reference has been made-to withdrawal of the paste fromseparator ll at temperatures ranging from 190 F. to 220 F. Suchtemperatures are definitely sterilizing to material like tomato paste.In fact, it is generally considered that temperatures above F. aresterilizing temperatures for tomato paste, although F. or higher isconsidered to be safer. Thus it may be said that my process carries outthe final evaporating step whereby the paste is withdrawn at asterilizing temperature.

It has been found that if the cans after being sealed are notimmediately tipped over, the.

small space'between the lid and the upper surface of the paste may notbe properly sterilized,

and therefore spoilage may occur, even though the paste may be at atemperature of 190 F. when it is introduced into the cans. When the cansare immediately tipped over after being filled and sealed, the lid ofthe can is immediately contacted with the hot paste, and completesterilization of the interior of the can takes place without resortingto additional heat treatment.

Tomato paste canned according to my process retains its fresh color andflavor, due to the fact that the treatment prior to introducing thematerial into the cans occurs at a rapid continuous rate with properregard to time and temperature factors, such as cause color and flavorimpairment.

grainy texture. The desirable body is attributed to a conditioning ofcertain gel forming ingredients oi.- the paste, such as pectin. Duringtreatment in the evaporator as described, the material is simultaneouslyconcentrated and subjected to over .a short intervalsterilizingtemperatures of time. a

This application is a continuation in part of my copending applicationSerial No. 223,682,

In addition the paste has a good body in that it will stand up whenpoured upon a fiat surface, and in that the surface has a paste to beproduced in said zone during formation of water vapor, supplyingsuflicient heat through the walls of said zone to maintain saidtemperature and cause formation oi. water vapor in said zone to producesaid concentrated paste, maintaining a high velocity of flow of saidstreams in said zone to produce a mixed vaporliquid phase material insaid zone, discharging the resulting mixture of concentrated paste andvapor from said zone and separating the sterilized concentrated pastefrom said vapor.

2. The process of preparing a concentrated and sterilized tomato pastefrom tomato pulp containing solids and water without substantiallyimpairing the color and body of the resulting paste, which comprises,passing the tomato pulp in a plurality of elongated flowing streamsthrough a heating zone, maintaining a. temperature between 190 and 220F. in said zone during formation of water vapor, supplying suflicientheat through the walls of said zone to maintain saidtemperature andcause formation of water vapor in said zone to produce said concentratedpaste, maintaining a high velocity of flow of said streams in said zoneto produce a mixed vaporliquid phase material in said zone, dischargingthe resulting mixture concentrated paste and vapor from said zone,separating the sterilized concentrated paste from said vapor.

3. The process of preparing a concentrated and sterilized tomato pastefrom tomato pulp containing solids and water without substantiallyimpairing the color and body of the resulting paste, which comprises,preheating the tomato pulp to a temperature of approximately 180 F.,passing the preheated tomato pulp in a plurality of elongated flowingstreams through a heating zone, maintaining a temperature between 190and 220 F. in said zone during formation of water vapor, supplyingsufllcient heat through the walls 01' said zone to maintain saidtemperature and cause formation of water vapor in said zone to producesaid concentrated paste, maintainingv a high velocity of flow of saidstreams in said zone to produce a mixed vaporliquid phase material insaid zone, discharging the resulting mixture of concentrated paste andvapor from said zone and separatingrthe sterilized concentrated pastefrom said vapor while at a sterilizing temperature.

v 4. The process of preparing a concentrated and sterilized tomato pastefrom tomato pulp containing solids and water without substantiallyimpairing the color and body 01' the, resulting paste, which comprises,passing the tomato pulp in a plurality of elongated flowing streamsthrough a heating zone, maintaining a temperature between 210 and 220 F.in said zone during formation of water vapor therein, supplyingsuflicient heat through the walls of said zone to maintain saidtemperature and cause formation of water vapor in said zone to produce aconcentrated paste containing at least 25% solids, maintaining arelatively high velocity of flow of said streams in said zone to producea mixed vapor-liquid phase material in said zone, discharging theresulting mixture of .conceno trated paste and vapor from said zone andsepcontainers.

arating the sterilized concentrated paste from said vapor while at asterilizing temperature, and cooling said concentrated paste to atemperature between approximately and F. preparatory to placed saidcooled concentrated paste in sealed DAVID D. PEEBLES.

